Impulse generator



April 2o, 1954 E. H. HUGENHOLTZ ET AL IMPULSE GENERATOR Filed Deo. 6, 1947 /o fmkm 6 n/ Patented Apr. 20, 1.954

IUNITED STATES PATENT oFFlcE IMPULSE GENERATOR Eduard ,Herman Hugenholtz and Johannes Hoogendoorn, Eindhoven, Netherlands, assignors toV Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application Decemter 6,1947,seria1No.790,14z

In the Netherlands September 16, 1946 sectioni, rubric Law 69o, August s, 1946 Patent expiresv September 16, 1966 If-an impulse lgenerator isrequired'to be used for controlling the frequency of a transmitter,-

it isgnaturally-necessary for the frequency of the impulse generator'itself to be kept within the narrowestpossible limits.V For this purpose use will-preferably be made of a quartz crystal.-

This'is possible, for example, by placing such a crystal in parallel with the frequency-determining circuit of a tube in the so-called transitron circuit-arrangement. This, however, sometimes gives rise to the undesirable phenomenon that the-frequency tends to jump back and forth between-the two valuesthat are determined by the crystal .andthe-said circuit (comp-rising if necessary, a single coil havnga stray capacity) respectively Y The invention has for Yits object to provide a crystal-controlledv impulse generator, in which the disadvantage just referred to cannot occur. According to the invention, use is made for this purpose-of the combination of an oscillatorcircuit-arrangement controlled by a crystal only and a so-called blocking oscillator.

Y OneI form of crystal Voscillator highly suitable for this purpose is the sol-called Pierce circuitarrangement which is to be understood'to mean a generator tube comprising a crystal connected between cathode and control-grid, a circuit connected between anode and cathode and substantiallytuned to the crystal frequency and in addition a coupling condenser between anode and control-grid. H

In order that the invention may be more clearly understood and readily carried into effect, it will now be-described more fully with reference to the accompanying drawing, in which Fig. l shows a, circuit-arrangement of the said kind which, however, according to the invention, is combined with. a blocking oscillator. For this purpose use is made of a multi-grid tube. i

The tube used according to Fig. 1 is a pentode P comprising grids I, 2 and 3 between a cathode 4 and an anode 5. Only a tube comprising the minimum number of crystal `grids required Vis,

shown for the sake of clearness of illustration. As an alternative, however, excellent results are obtainable with a heptode or pentagrid, in which the (screen) grid 2 is constructed so as to be double on either side of the grid 3 and in which provision is made in addition of afifth grid (suppressor grid) between anode and screen grid.

The-cathode 4 is earthed through a resistance 6 and a parallel condenser vhwhilst the grid I is also connected to earth through a crystal 8 Vand its leak resistance 9.

solaims. (c1. o-36) 1 minal of the anode voltage source.

2 vThe grid 2 acting as an anode is connected through a circuit comprising a coil VI Il and a tuning condenser II and through a resistance I2 and its smoothing condenser I3, to the positive terthis grid is coupled through a condenser Idto thegrid-I.

The circuit-arrangement hitherto described,

periods of lthe grid I the tube is blocked In addition, the anode circuit comprises a coil I5 which is tuned to a considerably higher frequency than the crystal 8, for example from l to 2 rnc./s. VThis coil is coupled to a coil- I6, oneY end of which is connected to the grid 2 and the` other end through a blocking condenser I? to' Lthe grid 3 which is earthed through a leakresistance I8.- The coil I5 may also, or else instead of coil I5 be tunedY tothe high frequencies.

This arrangement, to which the known principle of the blocking condenser is applied, enables: the system to oscillate periodically during only one period of the high natural frequency of the? coil I5 and/or I6 and for the rest periodicaily remains blocked due to the negative potential of the gridV 3. There are two causes for the latter fact: firstly the grid 3 is charged to a high negative value by .grid current at each current pulse passing through the tube and secondly, owing thereto the potential of the grid 2 decreases due to increase of the (screen) grid current, said de-y crease resulting, due to induction, in a further decrease of the potential of the grid 3 and so forth (transitron effect).

Consequently, at each passage of current through the tube, which, since the tube operatesl in class-C arrangement `and thus becomes conductive during a fraction only of each period of the crystal frequency, has the pattern of a current pulse, a highly ldamped oscillation of very high frequency occurs in the coils I5 and I5. This would occur each time when the potential of the grid lI passes through Zero, and hence twice in each period of the crystal frequency. In order to avoid this frequency-doubling, provisions may j ence to Fig. 2 in which at a the variations of the voltages' v1 and 'u2 across'the lericlsl and 2 respec-n In addition,

the voltage through Zero but not at the Ysecond passage through zero, since the .latter case the value of ci is below the cut-off value, which is indicated by the horizontal dotted line d.

As soon as the tube has become conductive, its top part starts to operate as a periodically'interrupted (blocking) oscillator, the grid 3 being charged during the first half-period of this .oscillation to such a negative value that there is no further oscillation. Thus, the circuit will oscillate out in a greatly damped manner, as is shown in Fig. 2b. Finally, Fig. 2o shows the variation of the impulses in the coil I5, which, being positive, are .adapted to be fed directly through a condenser IB to a load, for example a tube in C-arrangement.

. The time constant of the system l1, I8 is required to be Such that on the one hand the condenser H is discharged Within one period of the crystal (the frequency of which is, for example, 100 kc./s.) to such an extent as to allow the oscillation to start again, but that on the other hand after a half period the grid 3 still exhibits sufficient negative charge to keep this grid blocked, if the above mentioned phase displacement between the voltages at the grids l and 2 should be insuicient to suppress any second impulse. The desired variation .of the condenser voltage is shown iny Fig. 2b in dotted lines by the curves U17.

Finally, it may be desirable for a diode D to be connected between the ygrid. 3 and the cathode li, since otherwise passageV of the grid current towards this grid might be prevented by the grid I. The cathodes of the tubes P and D are directly interconnected and connected through. a resistance 25J to the positive terminal of the anode battery, so that an adequate amount of negative bias voltage is safeguarded under all conditions by'voltage drop across the resistance 6.

What we claim is:

l. An impulse generator comprising an electron discharge device provided with a cathode, a first grid, a second gridand a plate electrode, a crystal-controlled oscillatory circuit operating at a predetermined frequency .and including an electron discharge system .constituted by. the cathode, the rst .grid andthe second grid of said device and a piezo-electric crystal member coupled between said first grid and one of the other electrodes of said system, said first gridacting as a control grid in said system and said second acting as an anode in said system, a resonator element tuned to a frequency which is high relative to said predetermined frequency, means to apply a constant potential throughsaid resonator element to said plate, means coupled to said resonator element to derive a blocking voltage from said element each time after one oscillatory period thereof, and means to apply said. blocking voltage to an electrode of said device to render tron discharge device provided with a cathode.'

a first grid, a second grid and a plate electrode, a crystal controlled oscillatory circuit operating at a predetermined frequency and including an electron discharge system constituted .by the cathode, the rst grid and the second grid of said device, said first grid acting as a control grid and said second grid acting as an anode, a piezoelectricV crystal member connected between the cathode and the control grid of said system, a `tuned network-connected between the cathode andthe anode ofsaid system and a feedback capacitor connected between the anode and the control grid of said system, a resonator element tuned to afrequency Which is high relative to said predetermined frequency, means to apply a positive potential through said resonator element to said plate, means coupled to said element to derive a blocking voltage from said element each time after one oscillatory period thereof, and means to apply said blocking voltage to an electrode of said device vto render same non-conductive, whereby impulses are yielded at said plate at a repetition rate corresponding to said predetermined frequency.

3. A periodic impulse generator comprising an electron discharge device provided with a cathode, first, :second and third grids and a plate electrode, a crystal-controlled.oscillatory circuit operating at a predetermined frequency and including an electron discharge system constituted by the cathode, the first grid and the second grid of said device and a piezo-electric crystal member coupled between said cathode and said first grid of said system, said first-grid acting as a control grid in said systemand said second grid acting as an anode in said system, a resonator element tuned to a'frequency which is high relative to said predetermined frequency, means to apply a positive voltage through said resonator element to said plate, means coupled to said resonator element to derive a blocking voltage from said element each time after one oscillatory period thereof, and means to apply said blocking voltage to said third grid to render said device non-conductive whereby-impulses are yielded by said plate at arepetition rate corresponding to said predetermined frequency.

4. A periodic impulse generator comprising an electron discharge device provided with a cathode, rst, second and third grids yand a plate, in the order named, a crystal controlled oscillatory circuit operating at a predetermined frequency, said circuit including an electron discharge system constituted by said cathode, said first grid acting as a control grid and said secondy grid acting as an anode, a piezo-electric'crystal member connected between said cathode and said control grid, a tuned network connected between said cathode and said anode and a feedback capacitance connected between said anode and said control grid, a resonator .element and tuned to a frequency which is high relative to said predetermined frequency, means to apply a positive potentialthrough said resonator element to said plate, means coupled to said element to derive a blocking 'voltage from said element each time after one oscillatory period thereof, and means to apply said locking voltage to said third grid to render said device non-conductive whereby impulses are yielded by said plate at a repetition rate corresponding tofsaidpredetermined frequency.

5.,An arrangement as set forth :in claim 4, wherein said tuned network insaid oscillatory circuit is arranged to effect aphase displacement between the oscillatory voltages appearing on said control grid and on said anode to an extent at which current iiows through said discharge path in said device only once during each period of said predetermined frequency.

6. An arrangement as set forth in claim 4, wherein said means to derive a blocking voltage from said element comprises a coil inductvely coupled to said element, a blocking condenser connected in series with said coil between said third grid and said anode, and a resistance connected between said third grid and said cathode, said blocking voltage being developed across said resistance.

'7. An arrangement as set forth in claim 6 wherein the time constant of the resistance-capacitance network formed by said blocking condenser and said resistance has a value at which the blocking voltage developed across said resistance is erased in an interval falling between a half period and a full period of said predetermined frequency of said oscillatory circuit.

8. An arrangement as set forth in claim 7 further including a diode electron discharge device 6 connected between said cathode and said third grid.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,919,795 Marrison July 25, 1933 2,212,202 Faudell et al Aug. 20, 1940 2,215,776 Barnard Sept. 24, 1940 2,217,401 Geiger Oct. 8, 1940 2,230,097 Whitaker Jan. 28, 1941 2,373,223 Braaten Apr. 10, 1945 2,452,951 Norgaard Nov. 2, 1948 2,484,763 Sturm Oct. 11, 1949 2,540,524 Houghton Feb. 6, 1951 FOREIGN PATENTS Number Country Date 210,447 Switzerland July 15, 1940 OTHER REFERENCES Kirkman, 527,321, led March 20, 1944, published January 3, 1950, as abandoned application. (Abstracted in volume 630, O. G., page 282.) 

